Cathode ray tube with rear projection readout

ABSTRACT

A display tube for selectively providing a visual display of a plurality of characters, including a vacuum envelope with a display screen at one end thereof and a plurality of columns of first means providing a source of electrons at the other end thereof. An apertured mask disposed between the first means and the display screen energizable to accelerate the electrons into a different stream of electrons for each of the characters. A plurality of rows of grid control boxes disposed between the first means and the apertured mask each of the rows controlling a portion of the electrons provided by each of the columns of first means by inhibiting the effect of the apertured mask on the controlled portions. The rows of grid control boxes and columns of first means individually energizable so that a single stream of electrons is accelerated and a single one of the characters is displayed, wherein the number of characters displayable is equal to the product of the number of rows and the number of columns.

United States Patent 191 Gumpertz June 26, 1973 CATHODE'RAY TUBE WITHREAR PROJECTION READOUT Donald G. Gumpertz, Van Nuys, Calif.

[73] Assignee: Industrial Electronic Engineers, Inc.,

Van Nuys, Calif.

[22] Filed: Mar. 30, 1972 [21] Appl. No.: 239,535

[75] Inventor:

Primary Examiner-John Kominski Attorney-Ellsworth R. Roston et al.

[57] ABSTRACT A display tube for selectively providing a visual displayof a plurality of characters, including a vacuum envelope with a displayscreen at one end thereof and a plurality of columns of first meansproviding a source of electrons at the other end thereof. An aperturedmask disposed between the first means and the display screen energizableto accelerate the electrons into a different stream of electrons foreach of the characters. A plurality of rows of grid control boxesdisposed between the first means and the apertured mask each of the rowscontrolling a portion of the electrons provided by each of the columnsof first means by inhibiting the effect of the apertured mask on thecontrolled portions. The rows of grid control boxes and columns of firstmeans individually energizable so that a single stream of electrons isaccelerated and a single one of the characters is displayed, wherein thenumber of characters displayable is equal to the product of the numberof rows and the number of columns.

15 Claims, 4 Drawing Figures PAIENTEMunzs nan SHEHEUFB CATHODE RAY TUBEWITH REAR PROJECTION READOUT BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates generally to display tubes and morespecifically to means disposed in rows and columns and individuallyenergizable to provide a visual display of one of a plurality ofcharacters.

2. Background of the Invention The prior art includes vacuum tubeshaving display screens at one end thereof excitable by electronsimpinging thereon. At the opposite end of the tube a filament provides asource of electrons. A plurality of grid control boxes have been alignedin a single column with the filament extending through the column ofboxes. This combination has enabled each of the grid control boxes toenclose a portion of the electrons provided by the associated filament.

An apertured mask has been disposed between the grid control boxes andthe display screen, the mask having characteristics for being energizedto displace and accelerate in a stream of electrons each of the portionsof electrons associated with each of the grid control boxes. A charactermask has been disposed between the apertured mask and the display screento provide each of the streams of electrons with a cross-- sectionsimilar in shapeto one of the characters to be displayed.

Each of the grid control boxes has been provided with an aperturethrough which the enclosed portion of the electrons passes to form oneof the streams of electrons. The grid control boxes have beenindividually energizable to inhibit the effect of the energized aperturemask upon the portions of electrons enclosed by the energized gridcontrol box and thereby to inhibit the formation of the associatedstream of electrons.

A plurality of pins each connected to an individual one of the gridcontrol boxes have extended from the header at the rear of the displaytube to cooperate with a socket having portions thereof registerablewith each of the pins. The fact that an individual pin has been a usedfor each of the grid control boxes has been a major limitation inincreasing the number of characters that could be displayed by anindividual display tube. In part, this limitation has been a spatiallimitation on the header and the tube socket.

In addition, an individual switch has been associated with each of thepins of the display tube so that each of the grid control boxes could beindividually energized to inhibit all but a particular one of the gridcontrol boxes so that the character associated with the particular gridcontrol box would be displayed by the tube. This number of individualswitches has been expensive to purchase and maintain and the amount ofspace required for the switches has been relatively large in comparisonto the size of the'display tubes. Furthermore, the individual switcheshave been cumbersome to operate.

It can be appreciated that since individual pins and switches have beenassociated with each of the grid control boxes, the limitations if spaceand expense have been major factors in limiting the number of charactersdisplayable by the tubes of the prior art. In those situations whererelatively few characters have been desired, the foregoing limitationshave been minor and the tubes of the prior art have been satisfactory.

SUMMARY OF THE INVENTION The display tube disclosed .herein includes avacuum envelope having a display screen at one end thereof and aplurality of filaments arranged in columns at the opposite end thereof.Each of the filaments is energizable to provide a cloud of electronswhich can be formed into a plurality of streams of electrons byanapsidethereof. The grid control bars are stacked so that the apertures aredisposed in rows and columns.

Each of the filaments passes through a portion of each of the gridcontrol bars to associate with an individual column of the apertures. Inthis manner, each of the grid control bars encloses a portion of thecloud of electrons provided by each of the filaments. Thus, a'particular one of the filaments cooperates with a particular one of thegrid control bars to provide an individual portion of the cloud ofelectrons, which portion associated with one of the apertures in theparticular grid control bar to form one of the streams of electrons.

The filaments are individually energizable so that the only cloud ofelectrons formed is that associated with the energized filament. Thus,only those apertures disposed in the column of apertures associated withthe energized filament have characteristics for forming a stream ofelectrons.

Similarly, the grid control bars are individually energizable so thatonly those portions of the clouds of electrons which are enclosed in adeenergized grid control bar are capable of being formed into a streamof electrons. The apertured mask is energizable to form into a stream ofelectrons that portion of the cloud of electronsassociated with theenergized filament and the deenergized grid control bar. By individuallyenergizing one of the filaments disposed in a column and deenergizingone of the grid control bars disposed in a row, only electrons at aparticular position common to the individual row and the individualcolumn are able to move towards the screen. These electrons are thenformed into a stream and are shaped by an individual one of thecharacters on a characer mask to produce a display of that individualcharacter on the screen.

The advantages of this display tube are readily apparent. A singleconductor attached to each of the grid control bars is sufficient tocontrol the streams of electrons associated with a row of the apertures.Similarly, a single conductor attached to each of the filaments issufficient to control the streams of electrons associated with a columnof the apertures. Furthermore, a single switch and a single pin on theheader of the tube is sufficient to actuate one of the conductors. Ofultimate importance is the fact that a number of characters equal to theproduct of the rows and columns of apertures can be individuallycontrolled by a number of pins and switches substantially equal to thesums of the rows and columns of apertures. For example, 64 charactersassociated with 8 rows and 8 columns of apertures can be controlled by17 conductors and pins, and 16 switches. Not only is the amount of panelspace dedicated to the switches substantially decreased, but the numberof characters displayable by a given size of tube header issubstantially increased. With this increase in characters, a displaytube can accommodate a significant number of special characters inaddition to a full alphanumeric presentation. In short, this displaytube will provide an extremely high message density per square inch ofpanel space.

This and other features of the present invention will become moreapparent with a detailed description of the preferred embodiments incombination with the associated drawings.

DESCRIPTION OF THE FIGURES FIG. 1 is a fragmented perspective view ofone embodiment of the display tube;

FIG. 2 is a side elevational view of the display tube taken on line 2 2of FIG. 1;

FIG. 3 is a plan view of a portion of the display tube taken on line 3 3of FIG. 2; and

FIG. 4 is a front elevational view of the display tube taken on line 4 4of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENTS A display tube is shown generallyat in FIG. 1 wherein a vacuum envelope is designated generally by thereference numeral 11. The vacuum envelope 11 can be substantiallytubular in configuration with a forward end and a rearward end showngenerally at 13 and 15, respectively. The materials comprising thevacuum envelope 11 as well as the procedure for evacuating and sealingthe envelope are in accordance with conventional vacuum tubeconstruction practice. In the preferred embodiment, the vacuum envelope11 is formed from a tube envelope T12ZD1 which is the largestcylindrical standard size in the tube industry. It will be appreciated,however, that the invention can be embodied in other sizes of tubeenvelopes.

A plurality of fluorescent particles 17 are disposed on the interiorsurface of the vacuum envelope 11 at the forward end 13 thereof. Thefluorescent particles 17, which have characteristics for illuminatingwhen bombarded by electrons, can be viewed externally of the vacuumenvelope 1] to provide a display screen 19 at the forward end 13 of theenvelope 1!.

A plurality of electron flood guns shown generally at 21 are disposed atthe rearward end 15 of the vacuum envelope 11. Each of the electronflood guns 21 has characteristics for being controlled to accelerate inthe direction of the display screen 19 a stream of electrons, typifiedby the stream of electrons 23. A character mask 25, which is disposedbetween the flood guns 21 and the display screen 19, includes aplurality of apertures 27 each shaped in the form of a character anddisposed in the path of a particular one of the streams of electrons 23.As a particular one of the streams of electrons 23 passes through itsassociated aperture 27, its

cross section is altered so that the fluorescent particles 17 arebombarded in the shape of the associated aperture 27. In this manner, adesired one of the characters can be made visible on the display screen19.

The electron flood guns 21 include a plurality of sources of electronssuch as the filaments 29 which are aligned in columns at the rearwardend 15 of the envelope 11. The filaments 29 are individually energizabletoprovide a cloud of electrons 30 (shown best in FIG. 2) for each of thefilaments 29. A plurality of grid control bars 35 can provide means fordividing each of the clouds of electrons 30 into portions so that adifferent portion of electrons is provided for each of the electronflood guns 21. The grid control bars 35 can be spaced from each other inrows transverse to the columns of the filaments with a plurality ofapertures 37 individually spaced on each of the bars between anassociated one of the filaments 29 and the display screen 19. Thus, eachof the grid control bars 35 includes one of the apertures 37 for each ofthe filaments 29, so that the apertures 37 are disposed in rowscorresponding to the rows of the grid control bars 35 and columnscorresponding to the columns of the filaments 29.

Means for displacing at least one of the portions of the clouds ofelectrons from the grid control bars 35 comprises an anode mask 31preferably disposed between the filaments 29 and the character mask 26.The anode mask 31 includes a plurality of apertures 33 through one ofwhich each of the streams of electrons 23 passes. The anode mask 31 hasproperties for being energized at a potential such as 2,000 volts d-c todisplace and accelerate into the streams of electrons 23 the electronsprovided by the filaments 29. The amount of power consumed by theenergized anode mask is in the order of milliwatts.

Each of the grid control bars 35 has characteristics for beingseparately energized through one of a plurality of conductors 36 toinhibit the effect of the anode mask 31 on the portions of the clouds ofelectrons 30 enclosed by the energized grid control bars 35. When oneofv the grid control bars 35 is energized, it receives a voltage whichneutralizes the voltage normally applied to the bar to inhibit themovement of electrons past the bar. Since the grid control bar isneutralized, the electrons are attracted toward the anode mask by thepositive potential on the mask. In this way, by energizing only onefilament 29 and one grid control bar at any one time, only the cloud ofelectrons at one position represented by the intersection of thefilament and the bar is able to be attracted toward the screen 17 by thepositive voltage on the anode mask 31. Thus, the separate energizationof the filaments 29 and the grid control bars 35 enables the flood guns21 to be individually actuated so that the display on the screen 19 canbe limited to a single character. This single character is adjacent tothe position at which the energized filament and the energized gridcontrol bar have a common position in space.

Also shown in FIG. 1 is a getter shield 28 which is disposed at least inpart forwardly of the character mask 25 to inhibit the transit ofextraneous electrons from the rearward end 15 to the forward end 13 ofthe envelope 11. An end shield 32 is disposed over the ends of thefilaments 29 to inhibit the effect of the energized anode mask 31 uponthe electrons disposed outwardly of the rows of grid control bars 35. Tofurther insure that the electrons provided by the filaments 29 passforwardly only through the apertures 37, the spacing of the grid controlbars 35 can be limited to a distance such as 0.010 inches.

It can be appreciated that if the distance between the character maskand the screen is minimized, the focus of the characters upon the screenwill be improved. However, since the streams of electrons 23, which havea circular cross section after passing through the apertures 33, areeach centered upon the display screen 19, the streams of electrons 23tend to cross over at a particular distance from the grid control bars35. It is desirable that the character mask 25 be disposed rearwardly ofthe point where the streams of electrons 23 tend to cross over so that asingle stream of electrons 23 does not illuminate more than one of theapertures 27 in the character mask.

In the preferred embodiment, a rectangular mask 40 having a plurality ofrectangular apertures 42 disposed therein is located between the anodemask 31 and the character mask 25. Each of the streams of electrons 23passes through a different one of the apertures 42 so that the crosssection of the streams of electrons is made substantially rectangular.In this manner, the point at which the streams of electrons 23 crossover is extended beyond the particular distance. This enables thecharacter mask 25 to be located nearer the screen 19 and the form of thecharacters on the screen 13 is thereby improved.

The filaments 29 can comprise tungsten wire having a diameter ofapproximately 0.001 inches suspended between a pair of supports 39 ateither end of the filaments 29. The filaments 29 can be individuallyconnected through a plurality of filament switches, such as the switch41, to a source of potential 43. When one of the switches 41 is closed,current will flow through and heat the associated one of the filaments29. In the preferred embodiment, the source of potential 43 ismaintained at a value of 1.75 i 0.15 volts a-c/d-c at which voltage theenergized filament is heated to a temperature of approximately 850C.This temperature has been found sufficient to provide the cloud ofelectrons 30 about each of the energized filaments 29.

The supports 39 can be formed from a material such as mica having a lowheat conductivity and limited to a thickness such as 0.010 inches sothat a minimum amount of heat passes from an energized filament 29through its associated supports 39.

As shown in FIG. 2, each of the grid control bars can include portions45 defining a pair of apertures 46 for receiving each of the filaments29. Desirably the filaments 29 do not contact the portions 45 so thatheat is not dissipated to the grid control bars 35 when the filamentsare energized.

A plan view of an individual one of the grid control bars 35 is shown inFIG. 3. In the preferred embodiment, each of the grid control bars 35has one of a plurality of forward edges 49 each provided with a radiusof curvature substantially centered on the center of the display screen19. Each of the filaments 29 is aligned with a respective one of theapertures 37 is the grid control bars 35 and an associated one of theapertures 33 in the anode mask 31. Preferably, the filaments 29 areequidistant from the center of the display screen As the anode mask 31is energized, electrical lines of force 47 extend through the apertures37 into the grid control bars 35 to withdraw along the lines of force 47the electrons provided by the energized filaments 29. Unopposed, theelectrical lines of force 47 tend to accelerate into one of the streamsof electrons 23 each of the portions of the cloud of electrons 30provided by the energized filaments 29. Thus, each of the portions ofthe cloud of-electrons 30 is accelerated through an associated one ofthe apertures 37 in the grid control bars 35 and an associated one ofthe apertures 33 in the anode mask 31 to impinge upon the fluorescentparticles l7.

Each of the grid control bars 35 can be deenergized, or individuallyenergized through one of a plurality of switches 46 to either augment orinhibit the effect of the energized anode mask 31 upon the portions ofthe clouds of electrons 43 enclosed by the energized grid control bars35. For example, in an embodiment where the anode mask 31 is positivelyenergized, a grid control bar 35 can be energized with a negativepotential such as 6 volts d-c so that the electrical lines of force 47provided by the energized anode mask 31 are inhibited from extendingthrough the apertures 37 of the negatively energized grid control bars35. Thus, even though the negatively energized grid control bars 35 mayenclose portions of the clouds of electrons 30, the electrical lines offorce 47 may not-be capable of forming those portions into the stream ofelectrons 23.

In contradistinction, the grid control bars 35 can be individuallyenergized with a positive potential such as +4 volts d-c so that theelectrical lines of force 47 are reinforced in proximity to theapertures 37 to aid in formation of the streams of electrons 23. Apositive potential on the grid control bars 35 will provide anadditional advantage in improving the focus of the characters on thedisplay screen 19. Since the electrons tend to travel along the lines offorce 47 it is desirable to reduce the width of the lines of force 47 inproximity to the apertures 37 so that the streams of electrons 23appearto emanate from a point source. With a positive potential on the gridcontrol bars 35, the positive electrical lines of force 47 at theapertures 37 are reduced substantially to the configuration of a line48. Thus, the streams of electrons 23 appear to emanate from a pointsource on the line 48 and the focus of the characters is considerablyincreased.

In order to provide each character displayed on the display screen 19with a substantially uniform intensity, it is desirable that each of thestreams 'of electrons 30 have a substantially uniform electron densityand velocity when they impinge upon the fluorescent particles 17. In thepreferred embodiment, at least two dimensions are of importance inaccomplishing this result, the distance between the apertures 37 and thefilaments 29 and the distance between the anode mask 31 and the aperture37.

In the preferred embodiment the spacing of the filaments 29 and theassociated apertures 37 is maintained at a uniform distance such as .075inches. This uniform distance will aid in maintaining each of the cloudsof electrons 30 an equal distance from the apertures 37. It would bepossible to maintain this distance by aligning the forward edges 49 ofthe grid control bars 35 so that they substantially form an imaginaryspherical surface having a radius centered on the center of the displayscreen 19. Thus, the grid control bars 35 progressively spaced from thecentermost grid control bars 35 are progressively canted toward thecenter of the display screen 19 and displaced forwardly. In such aconfiguration, the filaments 29 could be supported at a plurality oflocations to define an imaginary spherical surface concentric with theimaginary spherical surface formed by the grid control bars 35. Thiswould maintain the desirable spacing between the apertures 37 and theassociated filaments 29.

In a preferred embodiment, each of the filaments 29 is disposed in alinear configuration between only a pair of the supports 39. Thus, thefilaments 29 substantially define an imaginary cylinder centered uponthe center the supports 39 is also reduced. Since heat is related topower, the foregoing advantages are particularly appreciated in the lowpower consumption of the display tube. The filaments 29 typicallyconsume only 1.3 watts of power.

It can be appreciated that if the forward edges 49 of the grid controlbars 35 substantially define a sphere as in the previous embodiment, andthe linear filaments substantially define a cylinder, as in the presentembodiment, the distance between the apertures 37 and the filaments 29will not be uniform. For this reason, after the grid control bars 35 areprogressively canted toward the center of the display screen 19, each ofthem can be displaced rearwardly so that the apertures 37 are spaced thedesired distance from the filaments 29. In this configuration, theapertures 37 are substantially disposed on an imaginary cylinderconcentric with the imaginary cylinder upon which the filaments 29 aredisposed.

The preferred distance between the anode mask 31 and the forward edges49 of the grid control boxes 35 is 0.050 inches. This uniform dimensionis desirable so that the electrical lines of force 47 extending throughthe apertures 37 will be of substantially equal intensity. In thepreferred embodiment where the grid control boxes are progressivelycanted and displaced rearwardly, the anode mask 31 is provided with aconfiguration similar to the combined configuration of the forward edges49 of the grid control boxes 35. Thus, the anode mask 31 is preferably asurface of revolution generated by revolving a zig-zag line such as theline 51 (shown in FIG. 2) about a radius equal to the distance betweenthe anode mask 31 and the display screen 19. With the anode mask 31 andthe forward edges 49 of the grid control bars 35 similarly configured,the apertures 37 in the grid control bars 35 and the associatedapertures 33 in the anode mask 31 are disposed in substantially parallelsurfaces which can be spaced the desired distance.

If the filaments 29 are uniformly heated and the anode mask 31 isuniformly energized, the mainenance of the foregoing dimension betweenthe apertures 37, the filaments 29, and the anode mask 31 will providethe streams of electrons 30 with substantially constant electron densityand acceleration.

A front elevational view of the grid control bars 35 is shown in FIG. 4.From this view it can be appreciated that each of the electron floodguns 21 is associated with an individual one of the apertures 37. Itwill also be noted that each of the apertures 37 is associated with aparticular one of the filaments 29 and a particular one of the gridcontrol bars.

In the preferred embodiment, for a particular one of the streams ofelectrons 30 to be formed, at least two conditions must be fulfilled.First, the associated one of the filaments 29 must be energized to formthe associated one of the cloud of electrons 30 so that the particularstream ofelectrons 23 will have a source of electrons. Second, theassociated one of the grid control bars 35 must be energized so that theelectrical lines of force 47 provided by the energized anode mask 31 arenot inhibited from extending through the associated apertures 37 toaccelerate the particular portion of the cloud of electrons 30. I

These two conditions provide the preferred embodiment with at least twomeans for inhibiting the formations of a particular one of the streamsof electrons 23.

Of particular significance is the fact that the first condition isassociated with the columns of the flood gun 21 and the second conditionis associated with the rows of the flood guns 21. Thus, a singlecharacter can be displayed on the display screen 19 by inhibiting allbut a particular one of the flood guns with either the first or secondcondition. Specifically, 'all but the associated one of the filaments 29can be deenergized, and all but the associated one of the grid controlbars 35 can be negatively energized. This can be accomplished with aminimum number of pins 38 on the header 34 of the tube and a minimumnumber of switches 41 and 46 on the panel, each substantially equal tothe sum of the filaments 29 and the grid control bars 35.

Although vacuum tube sizes which are economically available areparticularly adapted to receive eight grid control bars each containingeight apertures, it can be appreciated that a plurality of additionalelectron flood guns 21 can be added to the display tube 10 by theaddition of a single filament 29 or a single grid control bar 35. Ineither case the number of electron flood guns 21 could be substantiallyincreased with the addition of only a single pin 38 to the header 34 ofthe display tube.

This is of particular advantage since the number of flood guns 21, andthe number of associated characters which can be displayed by a displaytube is no longer dependent upon the number of pins 38 which can beaccommodated by the header 34 of the display tube. Since the number ofswitches 41 and 46 needed to individually actuate the electron floodguns 21 is substantially equal to the number of filaments 29 and gridcontrol bars 35, the amount of panel space needed to accommodate theswitches 41, 46is also decreased. It can also be appreciated that sincethe number of characters capable of being displayed by a display tube isincreased, themessage density per square inch of panel space is alsosubstantially increased. The foregoing advantages can be appreciatedwith a relatively low consumption of power.

While the present invention has been shown and described in what areconceived to be the most practical and preferred embodiments, it will berecognized by those skilled in the art that departures may be madetherefrom within the scope of the invention as set forth in thefollowing claims.

I claim:

1. A display tube for selectively providing a visual display of aplurality of characteris, comprising:

an envelope having a display screen including fluorescent particles atone end thereof;

a plurality of first means each providing a source of electrons, thefirst means disposed within the envelope at the end thereof opposite thedisplay screen and arranged in at least a pair of rows and a pair ofcolumns transverse to the rows to direct the electrons toward thedisplay screen;

second means disposed relative to the first means for forming into astream of electrons the electrons provided by each of the first means,the second means accelerating the electrons in the direction of thedisplay screen whereby the electrons impinge upon the fluorescentparticles to illuminate the display screen;

third means providing each of the streams of electrons generated by thesecond means with a cross section which is similar to the shape of anindividual one of the characters so that the display screen isilluminated in the shape of the individual character;

fourth means included in the first means and having characteristics forselectively controlling the formation of the streams of electronsassociated with a particular column of the first means;

fifth means included in the first means and having characteristics forselectively controlling the formation of the streams of electronsassociated with a particular row of the first means; whereby aparticular stream of electrons associated with the particular column andthe particualr row of the first means is generated by the second meansso that the particular character associated with the particular streamof electrons is displayed by the second means so that the particularcharacter associated with the particular stream of electrons isdisplayed by the display screen.

2. The display tube recited in claim 1, further comprising:

at least a pair of filaments included in the first means each of thefilaments having characteristics for being energized to provide a sourceof electrons for at least one of the columns of the first means; and

a plurality of first switching means included in the fourth means eachof the first switching means in series with one of the filaments forselectively energizing the filament associated with the particularcolumn of the first means. 7

3. The display tube asdefined in claim 2 wherein the fifth meansincludes:

a plurality of control boxes electrically connected to form at least apair of control bars, each control box having characteristics forsubstantially enclosing a portion of the electrons provided by anassociated one of the filaments; and

second switching means electrically connected to one of the controlboxes in each of the control bars for selectively energizing all but thecontrol bar associated with the particular row of the first means.

4. A display tube for selectively providing a visual display of aplurality of characters, comprising:

an envelope having a display screen including fluorescent particles atone end thereof;

a plurality of filaments disposed in columns relative to the displayscreen to direct electrons to the display screen, each filament havingcharacteristics for being energized to provide a source of electrons;

first means for selectively energizing a particular one of the filamentsso that the particular filament is a source of electrons;

a plurality of second means disposed in rows relative third means forselectively energizing all but a particular one of the second means tocontrol the passage of the electrons through the apertures in theenergized second means in accordance with such selective energizings;and

fourth means disposed between the second means and the display screenand having characteristics for being energized to displace from thefirst means in a stream of electrons the portion of electrons associatedwith the particular filament and the particular second means, the fourthmeans accelerating the electrons in the direction of the display screenand having characteristics to control the illumination of thefluorescent particles by the electrons passing through the second meansin accordance with a particular one of the characters.

5. The display tube as recited in claim 4 further comprising:

the energized fourth means creating first lines of force disposedrelative to the apertures of the particular second means to displace theportion of electrons associated with the particular filament;

the energized second means creating second lines of force having apolarity opposite that of the first lines of force and having at theapertures a magnitude greater than the magnitude of the first lines offorce; whereby the first lines of force are inhibited from passingthrough the apertures of the energized second means to displace theelectron enclosed thereby.

6. A display tube as defined in claim 5 wherein the apertures areprovided with a diameter sufficiently small to minimize the width of thefirst lines of force passing therethrough so that the free electrons intransit along the first line of force appear to emante from a point.

7. A display tube as defined in claim 5 wherein the second means arealigned with the fourth means so that the centermost portions of thecross sections of the respective streams of electrons coincide with thecenter of the display screen and the outermost portions of their crosssections tend to cross over at a particular distance from the secondmeans, the display tube further comprising sixth means disposed betweenthe second means and the fourth means for maximizing the particulardistance so that the distance between the fourth means and the displayscreen can be minimized to decrease the amplification of the particularcharacter.

8. A display tube as recited in claim 7 wherein the sixth meanscomprises:

a mask having portions thereof defining a plurality of apertures thereinthrough which each of the streams of electrons respectively passes, theapertures being substantially rectangular to shape the outermostportions of the streams of electrons so as to maximize the particulardistance.

9. In combination for selectively providing a visual indication of aplurality of characters comprising:

an envelope having a display screen at a forward end thereof;

at least a pair of filaments disposed interiorly of the envelope at arear end thereof and disposed relative to each other in a configurationcorresponding to the configuration of the display screen, each of thefilaments being energizable to form an individual cloud of electrons;

at least a pair of grid control bars each disposed in transverserelationship to the-filaments and in a particular spacing relative tothe filaments, and energizable to provide first characteristics forinhibiting the movement of a particular portion of the cloud ofelectrons from the associated energized filament and to provide secondcharacteristics for facilitating the movement of the particular portionof the cloud of electrons from the associated energized filament;

a first mask having a plurality of first apertures disposed between thegrid control bars and the display screen and in a particular spacingrelative to the grid control bars, the first mask being energizable tocreate a first electrical field having first lines of force relative toat least a particular one of the filaments for accelerating in thedirection of the display screen at least one stream of the electrons notinhibited by the grid control bars; whereby the accelerated electrons ineach of the streams of electrons impinge upon the display screen todisplay at least one of the characters.

10. The combination as recited in claim 9, the filaments beinglongitudinal in configuration and substantially parallel to each otherand the grid control bars being substantially arcuate in configuration.

11. The combination as recited in claim 10, each of the grid controlbars being disposed between the filaments and the display screen andbeing individually energizable to provide second characteristics forreinforcing the first lines of force produced by the first mask on theclouds of electrons provided by the filaments.

12. The combination as recited in claim 9 further comprising:

a plurality of grid control bars elongated in configuration and disposedsubstantially parallel to the other grid control bars with portions ofthe grid control bars extending between the filaments and the firstmask;

each of the grid control bars enclosing a portion of the cloud ofelectrons formed by each of the energized filaments, and

the grid control bars being selectively energizable to create a secondelectrical field having second lines of force resisting the accelerationof the electrons by the first lines of force.

13. The combination as recited in claim 12 further comprising:

a plurality of partitions disposed within each of the grid control boxesto form a plurality of compartments each having an open side facingrearwardly of the screen and a side defining a second aperture facingtoward the screen, each of the compartments substantially enclosing oneof the portions of the clouds of electrons; whereby second lines offorce inhibit the acceleration of the electrons through the secondapertures.

14. The combination recited in claim 9 including:

means for individually energizing the filaments;

means for individually energizing the grid control bars to provideindividual ones of the bars with the first characteristics at firstparticular times and with the second characteristics at secondparticular times different from the first particular times; and

means for energizing the first mask to create the first electricalfield.

15. The combination recited in claim 13 wherein the second apertures inone grid control boxes are equally spaced from the associated filamentand are equally spaced from the first mask.

t a aa s

1. A display tube for selectively providing a visual display of aplurality of characteris, comprising: an envelope having a displayscreen including fluorescent particles at one end thereof; a pluralityof first means each providing a source of electrons, the first meansdisposed within the envelope at the end thereof opposite the displayscreen and arranged in at least a pair of rows and a pair of columnstransverse to the rows to direct the electrons toward the displayscreen; second means disposed relative to the first means for forminginto a stream of electrons the electrons provided by each of the firstmeans, the second means accelerating the electrons in the direction ofthe display screen whereby the electrons impinge upon the fluorescentparticles to illuminate the display screen; third means providing eachof the streams of electrons generated by the second means with a crosssection which is similar to the shape of an individual one of thecharacters so that the display screen is illuminated in the shape of theindividual character; fourth means included in the first means andhaving characteristics for selectively controlling the formation of thestreams of electrons associated with a particular column of the firstmeans; fifth means included in the first means and havingcharacteristics for selectively controlling the formation of the streamsof electrons associated with a particular row of the first means;whereby a particular stream of electrons associated with the particularcolumn and the particualr row of the first means is generated by thesecond means so that the particular character associated with theparticular stream of electrons is displayed by the second means so thatthe particular character associated with the particular stream ofelectrons is displayed by the display screen.
 2. The display tuberecited in claim 1, further comprising: at least a pair of filamentsincluded in the first means each of the filaments having characteristicsfor being energized to provide a source of electrons for at least one ofthe columns of the first means; and a plurality of first switching meansincluded in the fourth means each of the first switching means in serieswith one of the filaments for selectively energizing the filamentassociated with the particular column of the first means.
 3. The displaytube as defined in claim 2 wherein the fifth means includes: a pluralityof control boxes electrically connected to form at least a pair ofcontrol bars, each control box having characteristics for substantiallyenclosing a portion of the electrons provided by an associated one ofthe filaments; and second switching means electrically connected to oneof the control boxes in each of the control bars for selectivelyenergizing all but the control bar associated with the particular row ofthe first means.
 4. A display tube for selectively providing a visualdisplay of a plurality of characters, comprising: an envelope having adisplay screen including fluorescent particles at one end thereof; aplurality of filaments disposed in columns relative to the displayscreen to direct electrons to the display screen, each filament havingcharacteristics for being energized to provide a source of electrons;first means for selectively energizing a particular one of the filamentsso that the particular filament is a source of electrons; a plurality ofsecond means disposed in rows relative to the filaments, each of thesecond means substantially controlling a different portion of theelectrons provided by each of the energized filaments, each of thesecond means having for each of the portions of electrons controlledthereby an aperture disposed between the associated filament and thedisplay screen; third means for selectively energizing all but aparticular one of the second means to control the passage of theelectrons Through the apertures in the energized second means inaccordance with such selective energizings; and fourth means disposedbetween the second means and the display screen and havingcharacteristics for being energized to displace from the first means ina stream of electrons the portion of electrons associated with theparticular filament and the particular second means, the fourth meansaccelerating the electrons in the direction of the display screen andhaving characteristics to control the illumination of the fluorescentparticles by the electrons passing through the second means inaccordance with a particular one of the characters.
 5. The display tubeas recited in claim 4 further comprising: the energized fourth meanscreating first lines of force disposed relative to the apertures of theparticular second means to displace the portion of electrons associatedwith the particular filament; the energized second means creating secondlines of force having a polarity opposite that of the first lines offorce and having at the apertures a magnitude greater than the magnitudeof the first lines of force; whereby the first lines of force areinhibited from passing through the apertures of the energized secondmeans to displace the electron enclosed thereby.
 6. A display tube asdefined in claim 5 wherein the apertures are provided with a diametersufficiently small to minimize the width of the first lines of forcepassing therethrough so that the free electrons in transit along thefirst line of force appear to emante from a point.
 7. A display tube asdefined in claim 5 wherein the second means are aligned with the fourthmeans so that the centermost portions of the cross sections of therespective streams of electrons coincide with the center of the displayscreen and the outermost portions of their cross sections tend to crossover at a particular distance from the second means, the display tubefurther comprising sixth means disposed between the second means and thefourth means for maximizing the particular distance so that the distancebetween the fourth means and the display screen can be minimized todecrease the amplification of the particular character.
 8. A displaytube as recited in claim 7 wherein the sixth means comprises: a maskhaving portions thereof defining a plurality of apertures thereinthrough which each of the streams of electrons respectively passes, theapertures being substantially rectangular to shape the outermostportions of the streams of electrons so as to maximize the particulardistance.
 9. In combination for selectively providing a visualindication of a plurality of characters comprising: an envelope having adisplay screen at a forward end thereof; at least a pair of filamentsdisposed interiorly of the envelope at a rear end thereof and disposedrelative to each other in a configuration corresponding to theconfiguration of the display screen, each of the filaments beingenergizable to form an individual cloud of electrons; at least a pair ofgrid control bars each disposed in transverse relationship to thefilaments and in a particular spacing relative to the filaments, andenergizable to provide first characteristics for inhibiting the movementof a particular portion of the cloud of electrons from the associatedenergized filament and to provide second characteristics forfacilitating the movement of the particular portion of the cloud ofelectrons from the associated energized filament; a first mask having aplurality of first apertures disposed between the grid control bars andthe display screen and in a particular spacing relative to the gridcontrol bars, the first mask being energizable to create a firstelectrical field having first lines of force relative to at least aparticular one of the filaments for accelerating in the direction of thedisplay screen at least one stream of the electrons not inhibited by thegrid control bars; whereby the accelerated electRons in each of thestreams of electrons impinge upon the display screen to display at leastone of the characters.
 10. The combination as recited in claim 9, thefilaments being longitudinal in configuration and substantially parallelto each other and the grid control bars being substantially arcuate inconfiguration.
 11. The combination as recited in claim 10, each of thegrid control bars being disposed between the filaments and the displayscreen and being individually energizable to provide secondcharacteristics for reinforcing the first lines of force produced by thefirst mask on the clouds of electrons provided by the filaments.
 12. Thecombination as recited in claim 9 further comprising: a plurality ofgrid control bars elongated in configuration and disposed substantiallyparallel to the other grid control bars with portions of the gridcontrol bars extending between the filaments and the first mask; each ofthe grid control bars enclosing a portion of the cloud of electronsformed by each of the energized filaments, and the grid control barsbeing selectively energizable to create a second electrical field havingsecond lines of force resisting the acceleration of the electrons by thefirst lines of force.
 13. The combination as recited in claim 12 furthercomprising: a plurality of partitions disposed within each of the gridcontrol boxes to form a plurality of compartments each having an openside facing rearwardly of the screen and a side defining a secondaperture facing toward the screen, each of the compartmentssubstantially enclosing one of the portions of the clouds of electrons;whereby second lines of force inhibit the acceleration of the electronsthrough the second apertures.
 14. The combination recited in claim 9including: means for individually energizing the filaments; means forindividually energizing the grid control bars to provide individual onesof the bars with the first characteristics at first particular times andwith the second characteristics at second particular times differentfrom the first particular times; and means for energizing the first maskto create the first electrical field.
 15. The combination recited inclaim 13 wherein the second apertures in one grid control boxes areequally spaced from the associated filament and are equally spaced fromthe first mask.